The effect of acute fluid consumption on measures of impedance and percent body fat estimated using segmental bioelectrical impedance analysis


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Abstract

Background/Objectives:To determine the effect of acute fluid consumption on measures of impedance and percent body fat (%BF) estimated using segmental bioelectrical impedance analysis (SBIA).Subjects/Methods:Seventy-six healthy, recreationally active adults (41 women; 35 men) volunteered to participate in this study (mean±s.d.; age, 21.0±1.6 years; body mass index, 25.0±3.2 kg/m2). Subjects had their body composition assessed on three separate occasions. After a baseline measurement, subjects consumed 591 ml of water (H2O), a carbohydrate/electrolyte drink (CHOE) or received nothing (CON). Subjects were reassessed 20, 40 and 60min following (POST) the baseline measure in each fluid condition.Results:Twenty minutes after drinking a H2O or CHOE beverage, %BF (1.1 and 1.2%), impedance (12 and 14Ω) and body mass increased significantly (P<0.001). During the CON trial, %BF (0.3 and 0.5%) and impedance (7 and 11Ω) also increased significantly above baseline values at 40 and 60min POST. However, the normal hourly variability was significantly (P<0.009) less than the observed fluid-induced %BF alterations. The greatest %BF increases were observed in the lightest subjects, who were women. Fluid type had no effect on the magnitude of change POST.Conclusions:Twenty minutes after drinking, %BF estimates increased approximately 1.0% due to elevations in impedance and body mass. As such, we recommend adhering to the pretest fluid restriction guideline to avoid fluid-induced alterations in SBIA body composition measures. In addition, use of a consistent testing schedule may minimize normal %BF variation over time.European Journal of Clinical Nutrition (2009) 63, 1115-1122; doi:10.1038/ejcn.2009.42; published online 17 June 2009

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